A Gamma Ray Race Through the Fabric of Space-Time Proves Einstein Right

By Eliza Strickland | October 29, 2009 4:48 pm

gamma-ray-burstNew results are in from the Fermi Space Telescope, which settled into orbit in the summer of 2008, and the findings seem to prove Albert Einstein right once again. Man, that guy was good.

The telescope detected and studied a gamma ray burst, one of the massively bright and powerful explosions that occurs when stars go supernova in distant galaxies. Astronomers were interested in the gamma rays of differing energies and wavelengths that were generated by the explosion, and that raced each other across the universe. After a journey of 7.3 billion light-years, they all arrived within nine-tenths of a second of one another in a detector on NASA’s Fermi Gamma-Ray Space Telescope, at 8:22 p.m., Eastern time, on May 9 [The New York Times].

The researchers were wondering if certain gamma rays with both high energies and short wavelengths would arrive last, at the back of the pack. That would suggest that they had violated one of the principles set out in Einstein‘s theory of relativity: that the speed of light is always constant. If researchers could detect a significant lag in some gamma rays, it would also give fresh hope to those ambitious researchers searching for a theory of everything.

At present, two separate theories dominate the world of physics. General relativity explains gravity and the motion of large objects such as planets, stars and galaxies, whereas quantum-mechanics explains the behaviour of very small things such as atoms. Both theories do well at explaining their respective worlds, but they don’t fit together mathematically. The problem is as fundamental as it gets: the two see space and time very differently [Nature News].

Einstein’s general relativity relies on space-time being smooth and continuous, while quantum mechanics suggests that the universe is made up of countless tiny grains of space-time. If the latter model is true, researchers theorized that the lumpy nature of space-time could interfere with the travel of some gamma rays. In simplified terms, that’s because higher energy photons have shorter wavelengths, which makes them more likely to bump into tiny lumps in spacetime and to be slowed by those structures. The slowdown would be tiny, but the lower velocity of high-energy photons could in principle be detectable over a journey of several billion light-years [Science News].

But the study of the Fermi Telescope’s results, published in Nature, declares that since all the gamma rays arrived within nine-tenths of a second apart, they must have all traveled at almost exactly the same speed. That suggests either that space-time is smooth and continuous, as general relativity proposed, or that the grains of space-time are smaller than we ever thought possible, and are having only the most minuscule effect on light waves. Researchers say the grains could theoretically be smaller than one-hundred-thousandth of a trillionth of the size of a proton [Science News].

Physicists working with the Fermi Telescope will keep looking for new evidence. But for now, says study coauthor Peter F. Michelson, “I take it as a confirmation that Einstein is still right” [The New York Times].

Related Content:
80beats: More Circumstantial Evidence for Dark Matter, But Debate Continues
80beats: Fermi Space Telescope May Follow the Gamma Rays to Find Dark Matter
80beats: New Space Telescope Has Already Found a Gamma Ray Mystery
80beats: First Map of the “Gamma Ray Universe” Produced

Image: NASA. Gamma ray bursts are the universe’s brightest explosions.

CATEGORIZED UNDER: Feature, Physics & Math
  • Stevie

    Ahhh .. Do you want Fries with that ? …

  • http://www.dnusbaum.com Doug Nusbaum

    John and Mary both arrived at my house at the same and they both left from the same apartment, so they both traveled at the same speed. And no one sees any problem with that?
    How about Mary stopped to put on lipstick so she left 1/2 hour after john.

    Exactly how was it determined that the high and low energy gamma rays left the source at the same time? That point was not even raised. Perhaps the editors think that we consumers of discover science are to dumb to understand these nuances?

  • Kin

    Apparently Doug is (too) to consider it [and I only say so rudely because I think his wording was rude], but I do believe they mention the explosion. It is “the” explosion not explosions that created the gamma rays.

    So they came from the same source and same moment.

  • deadnoon

    maybe the different route with difierent speed

  • chubbee

    “they must have all traveled at almost exactly the same speed. That suggests either that space-time is smooth and continuous, as general relativity proposed, or that the grains of space-time are smaller than we ever thought possible”
    Or that possibly they all traveled through the same space “terrain” on their way from point of origin to here, thereby encountering the same intervening forces?
    Dare I say, Duh?

  • YouRang

    The part that I find strange is: Is there no large mass approximately between here and the explosion? I.E. gravitational lensing from relatively small masses doesn’t ordinarily generate multiple signals since the source is so uniform. If the source is highly confined in time, one should expect that there would be multiple lensing events. Indeed how many bursts associated with high mass objects are the mirage from a more distant object whose primary signal arrived some time ago. At 1 second separation from straight on, the delayed signal would arrive several hundred thousand years earlier. Admittedly the cross section is small; but the payoff in terms of relative distances would be huge.
    With the usual quoted number of 100 *10^9 galaxies within 13 billion lyrs, we get about 10 billion galaxies within 7 billion lyrs. Assume all galaxies at an average distance of 5 billion lyrs, Then each galaxy occupies radius about 10^5 lyrs circle. So a black hole at the center of that galaxy is within 10^5/7*10^9 rads of the straight path. Hmm that’s still about a second. Astronomers don’t see as finely as I thought.
    Even if they had found a difference, the long wavelength inhomogeneities in space should make shorter wavelengths arrive earlier. After all if you fire a gamma ray and a visible ray through glass at an angle, the gamma ray would go straight thru and the visible would be diffracted both because of the path integral summation. So the null result can just be the result of competing disadvantages for long wavelengths and short wavelengths.

  • AlanM

    Doug #2, two reasons (I think).

    1. We have a pretty good idea of what generates the gamma rays and they would have been generated at the same time by our theories
    2. If they were generated at different times then it would be a truly mind-melting coincidence for them to arrive at the same time on Earth. John and Mary were both told to be at your place at 4PM, so it’s not so surprising that different start times resulted in the same arrival time. Of course, mind-melting coincidences *do* happen, which is why this experiment should be replicated (not that it wouldn’t have been anyway).

  • amphiox

    #5: “Or that possibly they all traveled through the same space “terrain” on their way from point of origin to here, thereby encountering the same intervening forces?”

    Actually chubbee, that was the whole point. The hypothesis being tested was that spacetime was “grainy” enough that the high energy short wavelength photons would experience a “different” terrain en route than the longer wavelength lower energy photons – for a short wavelength photon, a small irregularity is a large obstacle, while for a long wavelength photon, the same sized irregularity might was well not be there. Think of listening for FM and AM radio waves broadcast from the same point. The AM radio can be detected from further away because the longer wavelengths pass over obstacles that the shorter FM wavelengths get blocked.

    The hypothesis was not confirmed, meaning that the “graininess” of the intervening spacetime must have been so small that the high energy short wavelengths pass by unimpeded the same as the low energy long wavelengths (ie, relative to the “graininess”, even the short high energy wavelengths are long), thus giving the theoretical upper limit to the size of the hypothesized “graininess” that the researchers report.

  • Ashchaya

    I see no proof here. The fact that they’re 0.9s apart contradicts the very point of the article that they supposedly travelled at the same speed. So desperate are so many to cling to humble Einstein’s theories that they put blinkers on to make it so.

    Popular science is so unscientific it makes me sad. “Close enough, eh guys?”

  • Measuring Cup

    Or, perhaps time is simply a man made measurement that can only be used once in space and space is real. Therefore there are no grains of space-time. Only a measurement of how much time is needed to go through space.

  • Seagull

    #9: The fact that they are 0.9s apart supports the idea that either there is no granularity or that it is so small that it doesn’t affect the shorter wavelenghts as quantum theories suggested. If the granularity was on the order of size predicted by quantum theories, the separation would have been more than 0.9 seconds. Keep in mind that this light travelled 7,300,000,000 light years, and that the initial explosion was not instantaneous (and in fact could have thrown off different ‘layers’ of gamma ray energies at slightly different times). The study here is within its acceptable error range.

  • Brian Beverly

    Einstein cannot be ‘proved right’, however, we can falsify him. Fortunately for quantum physicists cosmologists understand stellar structure evolution and the early universe perfectly. The experimental error in cosmology is so small that there is virtually no background noise. Why no discussion of their error analysis? Has everyone checked their work?

    If space time is grainy then do you see any potential problems or bias by already referring to the quanta of light only in terms of their wavelengths? The fact that no one has mentioned integer multiplies of the ground state worries me. The data may falsify a discrete space-time but this article and the publicity for Einstein is dogmatic, when was the last time a null experiment was published in the NYT? I smell a rat.

    Can science move past hero worship?

  • Ashchaya

    Seagull Says: “Keep in mind that this light travelled 7,300,000,000 light years, and that the initial explosion was not instantaneous (and in fact could have thrown off different ‘layers’ of gamma ray energies at slightly different times). The study here is within its acceptable error range.”

    Nice blinkers.

  • John Miesner

    0.9 second in 7.3 billion years is 0.99999999999999999 agreement. Is someone trying to say that this is not an acceptable error? Have you ever heard of anything being measured to this accuracy? Of course you can’t prove Einstein right but he has been proven closer to right than anything else has ever been in all of human history.

  • WhatDoWeKnow

    So what is the probability if we didn’t observe?

  • BohrStein

    What worries me is that the rays didn’t arrive at the exact same time.

    Neither of the theories proved right nor wrong. However, something is
    going on that isn’t understood. A good place to be for a scientist.

    The only thing proven here is:

    The writer of this article has room for improvement in scientific reasoning.

  • Joseph (Wietchpec Joe) Kinz Jr.

    What I, as a lay person with an interest in physics, mathematics and cosmology, find most disturbing is that other lay persons feel themselves qualified to interpret, much less criticize, a professor (PhD) in these subjects. I prefer to listen intently and astutely to the professionals. Thanks folks.

  • Flexico

    #17~ THANK you! These peeps were starting to give me a headache! XD Mostly the snobbish attitude more than the iffy critique. True genius always has more questions than answers. Seems some people think the internet is the perfect place place to get an illusion of 15 minutes of fame.

  • myhikingboots

    Not to get off topic, but kudos to the research and the researchers. This is a significant tiny piece of the big picture that we seem to be closing in on. With the new Large Hadron Collider coming online and starting to collect data, a complete unified theory could be just around the corner. What an exciting time to be alive!

  • Aaron

    The thing is, even though this is a supernova, the two gamma rays may not have been given off at the same time. They could possibly have been released .09 seconds within each other, proving Einstein right. They could have been released at exactly the same millisecond and been affected the “grains” of space. Either way this helped me a lot in research for my project about the fabric of the space-time continuum.


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